In image display devices (e.g., liquid-crystal displays, organic EL displays, plasma displays, etc.) provided to various appliances (e.g., televisions, personal computers, smartphones, mobile phones, etc.), if external light such as light from indoor illuminators (e.g., fluorescent lamps) or sunlight is reflected in the screens, the visibility is reduced by the reflected images. In recent years, image display devices having a curved or bent screen are coming to be used, and inhibition of the reflection in the screen has become more important.
As a method for inhibiting the reflection of external light, there is a method in which an antiglare film having a surface with a rugged structure is disposed on a screen of an image display device to diffusedly reflect external light to thereby blur the reflected image.
Known as a method for forming an antiglare film is a method in which a composition containing a silica precursor such as a hydrolysis and condensation product of an alkoxysilane is applied to a substrate by spraying and fired (see, for example, Patent Document 1). In the case of forming an antiglare film by spraying, a two-fluid spray nozzle is frequently used.
However, it is necessary, for forming a homogeneous antiglare film, to employ a robot for scanning with the two-fluid spray nozzle, resulting in an increased cost and a prolonged coating period. In addition, the antiglare film thus obtained has insufficient homogeneity, and it has been difficult to obtain desired properties.
Meanwhile, Patent Document 2 proposes a method in which a surfactant is incorporated into a composition to render the liquid easy to spread and this composition is applied to a curved or bent substrate. There is a problem in that since a surfactant is used in a large amount to regulate the makeup of the composition so as to attain desired surface tension, not only an antiglare film having desired optical properties is not obtained but also the antiglare film thus obtained has insufficient optical evenness.
Patent Document 3 discloses a method for producing a curved substrate with an antiglare film, the method including steps of forming on a flat glass plate an antiglare film having a higher glass transition temperature than the flat glass plate and then forming a bent portion in the flat glass plate at an elevated temperature to produce a curved substrate with an antiglare film. The method in which the flat glass plate having an antiglare film formed thereon is shaped to form a bent portion in a part of the glass plate has a problem in that the flat portion and the bent portion differ in appearance. This is because the glass plate on which an antiglare film has been formed is exposed to a high temperature during the molding, in particular, an area where a bent portion is to be formed is heated to a temperature higher than that of the flat portion, and this heating damages a structure of the antiglare film. Furthermore, since an antiglare film having a glass transition temperature higher than the flat glass plate is formed, there is a problem in that in the molding step, the antiglare film itself has insufficient flexibility and a large number of defects, such as cracks, occur.
In addition, there is a problem in that the presence of an antireflection film disposed on a curved substrate results in differences in reflected-light color tone depending on a direction of viewing. There has been a problem in that in cases where a viewer views the display device from a position directly opposite to the screen, the screen has different color tones depending on portions of the curved substrate (see, for example, Patent Document 4).